Systems and methods for improving safety and resilience of electric circuits and electric grid infrastructure

ABSTRACT

An apparatus and methods are disclosed for monitoring the operation of an electrical power-transfer system and detecting and handling hazardous and undesirable system states. In accordance with one embodiment, an electrical signal is injected into the electrical power-transfer system. During or after the injection of the electrical signal, the following arc measured, (1) an electrical property between a first sensor and a second sensor to obtain a first measurement, (2) the electrical property between the second sensor and a third sensor to obtain a second measurement, and (3) the electrical properly between the first sensor and the third sensor to obtain a third measurement. The electrical power-transfer system is determined to be in a hazardous state based on the first measurement, the second measurement, and the third measurement, and in response to the determination one or more actions are performed to correct the hazardous state.

STATEMENT OF RELATED APPLICATIONS

The present application claims priority to, and incorporates fully byreference, U.S. Provisional Patent Application No. 63/024,659 filed May14, 2020.

FIELD OF THE INVENTION

The present disclosure relates to electrical power-transfer systems.

BACKGROUND OF THE INVENTION

Electrical power-transfer systems are capable of supplying power to andcharging devices such as smartphones, electrical vehicle (EV) chargers,etc. Such systems may possess defects and/or develop faults that posesafety hazards, potentially leading to fires, electrocution, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a block diagram of a system comprising an electricalsource, an electrical load, and a power-transfer monitoring device, inaccordance with one embodiment of the present disclosure.

FIG. 2 depicts a block diagram of sensor array 125-i, as shown in FIG.1, in accordance with one embodiment of the present disclosure.

FIG. 3 depicts a block diagram of environmental sensors 230-i, as shownin in FIG. 2, in accordance with one embodiment of the presentdisclosure.

FIG. 4 depicts an example installation of power-transfer monitoringdevice 110, as shown in FIG. 1, in accordance with one embodiment of thepresent disclosure.

FIG. 5 depicts a flow diagram of aspects of a method for detecting andhandling a hazardous state of an electrical power-transfer system, inaccordance with one embodiment of the present disclosure.

FIG. 6 depicts a flow diagram of aspects of a method for detecting andhandling an undesirable state of an electrical power-transfer system, inaccordance with one embodiment of the present disclosure.

FIG. 7 depicts an example impulse response characteristic in accordancewith one embodiment of the present disclosure.

FIG. 8 depicts an example of a typical diurnal pattern for temperaturein accordance with one embodiment of the present disclosure.

FIG. 9 depicts an example of a power-transfer cycle during a servicesession in which an electrical load is connected to an electricalpower-transfer system, power is transferred to or consumed by theelectrical load during the connection, and the electrical load issubsequently disconnected, in accordance with one embodiment of thepresent disclosure.

DETAILED DESCRIPTION

Embodiments of the present disclosure are capable of monitoring theoperation of an electrical power-transfer system and detectingundesirable and hazardous states of the system. For the purposes of thisdisclosure, the term “electrical power-transfer system” is defined as anapparatus comprising one or more electrical sources and one or moreconductors connected to a power-consuming load. (For convenience andbrevity, “electrical power-transfer system” may sometimes be referred tosimply as a “power-transfer system”).

For the purposes of this disclosure, the term “hazardous state” of anelectrical power-transfer system is a state in which one or both of: (1)the system is unsafe as a result of an event-in-progress or an eventthat has already occurred (e.g., a fire, an earthquake, etc.); and (2)the system has a vulnerability that makes the electrical power-transfersystem susceptible to unsafe events. It should be noted that the eventtriggering the hazardous state might by caused by the system itself(e.g., a fire resulting from conductor corrosion, etc.), or might be anexternal event (e.g., an earthquake, a flood, etc.). Embodiments of thepresent disclosure therefore can provide early warnings of future unsafeevents.

For the purposes of this disclosure, the term “defect” is defined as apre-existing flaw. In particular, a defect in a power-transfer system isdefined as a flaw in one or more elements of the system (e.g., aconductor, insulation, etc.) that may be present prior to operation ofthe system. Defects may be due, for example, to defective productmaterials; product manufacturing defects (e.g., missing strands in aconductor, loose wire strands, improper coiling, improperly-sizedconductor crimp, improperly-sized insulation crimp, improper striplength, improper wire insertion, excessive terminal bending, impropercrimp positioning, improperly-sized bellmouth, improper carrier cut-offlength, bent lock tangs, incomplete lock tangs, misaligned lock tangs,conductive dust, crimp contamination prior to use, corrosion prior touse, interference with connector mating [“terminal butting”], loosefastener screws, incomplete fastener encirclement, etc.); damage fromhandling and/or installation (e.g., nicks, strand twist damage, bendingstress damage, kink damage, etc.); and so forth.

For the purposes of this disclosure, the term “fault” is defined as aflaw that arises during operation of a system, either spontaneously ordeveloping over time. Faults in a power-transfer system may arise, forexample, as a result of abrasion, vibration, wear, operational stress,component aging, changing environmental conditions, animal chewing,corrosion (e.g., due to moisture, salt, degradation of an interfacebetween dissimilar metals, etc.), sparking, high-energy charges,overcurrent, magnetic susceptibility (e.g., current leakage paths andshort circuits due to metallic ferrous particles, etc.), overheating,seasonal environmental stress, diurnal environmental stress, and soforth.

In some instances, defects/faults in a power-transfer system may behidden or inaccessible. For example, a defect/fault may be buriedunderground, embedded in concrete work, located behind a wall, locatedunder a floor, located above a ceiling panel, and so forth. Thesedefects/faults may be exposed by particular events, such as powersurges, changing environmental conditions, etc.

Improvements to electrical distribution systems have been made in recentyears, including the deployment of ground-fault-circuit-interrupters(GFCIs) and current monitoring transformers paired with current-limitingcircuitry. These improvements, however, still fail to guard againstfailure modes such as latent and time-varying latent hazards. Thesefailure modes were once rare but have become more prevalent with theproliferation of modern mobile appliances that are frequently rechargedat high current levels. Mobile appliances are transported betweenlocations and may be connected opportunistically or haphazardly towell-worn connectors. This has made the new failures mode much morecommon. The higher frequency has increased the probability of occurrenceand therefore increased the risk of this hazard class.

A system may appear safe, but the connection of novel devices with newoperating characteristics may violate the safe operating envelopewithout warning, with unanticipated consequences. Further, modern mobileappliances can present dynamic and often dramatic shift in power demand.A case in point is electric vehicles whose appetite for power can exceedthe capacity for most fixed electrical systems. In this case, thedevices nearly always challenge the upper capacity limits of thestationary infrastructure to which they connect.

FIG. 1 depicts a block diagram of an electrical power-transfer system100, in accordance with one embodiment of the present disclosure. Asshown in the figure, electrical power-transfer system 100 comprises apower-transfer monitoring device 110 that is inserted between anelectrical source 170 (e.g., a battery, a solar array, a connection to autility grid, a distribution panel, etc.) and a power-consumingelectrical load 190 with battery storage (e.g., an EV charger, etc.),thereby forming a conducting path electrical source 170->power-transfermonitoring device 110->electrical load 190 that transfers power fromelectrical source 170 to electrical load 190, thereby “charging”electrical load 190. In one embodiment, electrical source 170 comprisesa branch circuit that is protected by a circuit breaker.

In one example, electrical source 170 is stationary and electrical load190 is a mobile appliance (e.g., a mobile electrical vehicle [EV], alawn mower, a wheelchair, etc.) that can be connected to anddisconnected from power-transfer monitoring device 110, or, whenpower-transfer monitoring device 110 is not present, can be connected toand disconnected from electrical source 170. Electrical load 190 is aconsumer of electric power, and typically incorporates storage forfuture use when disconnected from the electrical source. As will beappreciated by those skilled in the art, in some embodiments electricalsource 170 might supply power via alternating current (AC), while insome other embodiments electrical source 170 might supply power viadirect current (DC).

In some embodiments, electrical load 190 is capable of protecting itsinternal battery by either accepting charging current or by blockingpower. Admittance (charging) or rejection (non-charging) is accomplishedwith a built-in power conversion device or a BMS (Battery ManagementSystem), which are incorporated in some electrical loads for safety,longevity, and self-protection. In AC power systems, the poweradmittance involves a conversion from AC (incoming line) to DC (forbattery energy storage). With modern converters, the rate of powerconversion is controllable or “dispatchable.”

Electrical power-transfer system 100 further comprises a status device150 that is capable of receiving signals from processor 130 indicatingthe operational status of the system, thereby facilitating diagnosticoperations. In some implementations, the signals may also be used forsetup and parametric adjustment of installation-specific parameters(e.g., electrical properties such as operating voltage; system capacity;response time; AC or DC operation, etc.), as well as for specificationof environmental operating characteristics (for example, at the time ofinstallation).

In some examples, status device 150 might be a display (e.g., a textdisplay, a graphical user interface (GUI) touchscreen, etc.), while inother examples status device 150 might be an on/off indicator light,while in still other examples status device 150 might be some other typeof transducer such as a speaker, while in yet other examples statusdevice 150 might be a wireless or wireline conduit (e.g., a Wi-Fi basestation, etc.) that can connect to a smartphone or other type of device.In one embodiment, communication between processor 130 and 150 is via aserial-interface data communication line.

As shown in FIG. 1, power-transfer monitoring device 110 compriseslanding points 120-1, 120-2, and 120-3, sensor arrays 125-1, 125-2, and125-3, processor 130, memory 131, clock 132, and transceiver 140,interconnected as shown. The landing points 120-1, 120-2, and 120-3 areconnected to electrical source 170 via respective conductors 180-1,180-2 and 180-3, and are connected to electrical load 190 via respectiveconductors 185-1, 185-2 and 185-3. The points provide mechanicalstability and an electro/acoustic/thermal conductive reference. In someembodiments, landing points 120-1, 120-2, and 120-3 might beelectrically-conductive terminals, while in some other embodimentslanding points 120-1, 120-2, and 120-3 might be mechanically clamped orcrimped on to conductors 180/185, while in yet other embodiments landingpoints 120-1, 120-2, and 120-3 might be connected to conductors 180/185via a combination of these techniques (for example, landing point 120-1is an electrically-conductive terminal, landing point 120-2 ismechanically clamped to conductors 180-2 and 185-2, and landing point120-3 is mechanically crimped to conductors 180-3 and 185-3.

In some embodiments conductors 180 might be solid wires, while in someother embodiments conductors 180 might be stranded wires, while in stillother embodiments conductors 180 might be something else (e.g., cables,bus bars, printed circuit traces, etc.). In some embodiments, conductors180-1/180-2/180-3 might be uniform in type (e.g., all three conductorsare solid wires, all three conductors are stranded wires, etc.), whilein some other embodiments conductors 180-1/180-2/180-3 might vary intype (e.g., two of the conductors solid wires and one conductor strandedwire; one conductor a solid wire, one conductor a stranded wire, and oneconductor a cable; etc.). In addition, in some embodiments conductors180-1/180-2/180-3 might be insulated, while in some other embodimentsconductors 180-1/180-2/180-3 might be uninsulated, while in still otherembodiments, one or two of the conductors might be insulated and theremaining conductor(s) uninsulated.

Landing points 120 are further connected to electrical load 190 viaconductors 185-1, 185-2 and 185-3, which deliver power to electricalload 190. Conductors 185-1, 185-2 and 185-3, like conductors 180-1,180-2 and 180-3, may be solid wires, stranded wires, cables, bus bars,printed circuit traces, etc. In some embodiments, conductors185-1/185-2/185-3 might be of the same type, while in other embodimentsconductors 185-1/185-2/185-3 might vary in type. In addition, in someembodiments conductors 185-1/185-2/185-3 might be insulated, while insome other embodiments conductors 185-1/185-2/185-3 might beuninsulated, while in still other embodiments, one or two of theconductors might be insulated and the remaining conductor(s)uninsulated.

In some examples, a conductor 180-i might comprise a plurality ofconducting segments joined via one or more junction points (e.g., asafety box that contains a splice, a busbar, a branch connection point,etc.). In some such instances the segments might be of the same type(e.g., all are solid wires, etc.), while in other instances the segmentsmight vary in type. Similarly, in some instances the number and type ofsegments might be the same for all three conductors 180, 180-2 and180-3, while in other instances the number of segments might vary, orthe type of segments might vary, or both.

In some examples, a conductor 185-i might , like conductor 180-i,comprise a plurality of conducting segments joined via one or morejunction points. In some such examples the segments might be of the sametype (e.g., all are solid wires, etc.), while in other instances thesegments might vary in type. Similarly, in some examples the number andtype of segments might be the same for all three conductors 185-1, 185-2and 185-3, while in other instances the number of segments might vary,or the type of segments might vary, or both. The above examples may betrue, for example, when one or more connectors and/or one or more plugreceptacles are present.

In some examples, each conductor 185-i might be of the same compositionas respective conductor 180-i, while in other examples, one or more ofthe conductors 185 might be of a different type than respectiveconductor(s) 180. Further, in some embodiments conductors 185-1, 185-2and 185-3 might be insulated, while in some other embodiments conductors185-1, 185-2 and 185-3 might be uninsulated, while in still otherembodiments, one or two of the conductors might be insulated with theremaining conductor(s) uninsulated.

In one embodiment, conductors 180-1 and 185-1 are positive (or “hot”)conductors, conductors 180-2 and 185-2 are negative (or “return”)conductors, and conductors 180-3 and 185-3 are neutral reference (or“safety earth”) conductors. It should be noted that some otherembodiments might use only two conducting paths, rather than threeconductive paths (i.e., two landing points 120-1 and 120-2, respectivesensor arrays 125-1 and 125-2, and respective conductors 180-1/185-1 and180-2/185-2). This might be a viable option for certain low-cost ornon-critical applications, however a two-conductor arrangement isgenerally less desirable. In particular, such systems will not complywith modern safety codes, and have reduced perceptive capability thatmay reduce system performance. In addition, redundancy, which isbeneficial for self-calibration and self-test purposes, in reduced intwo-conductor systems compared to three-conductor systems.

It should further be noted that some other embodiments might use fourconducting paths rather than three (e.g., for a three-phase circuit,etc.). Such embodiments could comprise four landing points 120-1, 120-2,120-3 and 120-4, respective sensor arrays 125-1, 125-2, 125-3 and 125-4,and respective conductors 180-1/185-1, 180-2/185-2, 180-3/185-3, and180-4/185-4.

Each sensor array 125-i is capable of obtaining measurement datapertaining to one or more parameters (for example, one or more values ofone or more measured properties; a function of one or more values of oneor more measured properties, such as a rounding function, an averagingfunction, a differential over time [e.g., a high-pass filter, etc.]; andso forth), and is further capable of providing these data to processor130. In one embodiment, sensor arrays 125 are integrated circuits thatcommunicate with processor 130 via a shared serial bus. The compositionof sensor arrays 125 and their associated parameters in one embodimentare described in detail below with respect to FIGS. 2 and 3.

Processor 130 is capable of receiving data from sensor arrays 125 andperforming the methods of FIGS. 5 and 6 described below. In oneembodiment, processor 130 is a special-purpose processing device such asa digital signal processing (DSP) microcontroller, an applicationspecific integrated circuit (ASIC), a field programmable gate array(FPGA), or the like. In some other embodiments, processor 130 may be ageneral-purpose processing device, such as a microprocessor, centralprocessing unit, or the like. More particularly, processor 130 may be acomplex instruction set computing (CISC) microprocessor, a reducedinstruction set computing (RISC) microprocessor, a very long instructionword (VLIW) microprocessor, a processor implementing other instructionsets or combinations of instruction sets, or the like. Such processorsmay execute instructions stored in memory 131, including instructionscorresponding to one or more blocks of the methods of FIGS. 7 through 13described below, read data from memory 131, and/or write data to memory131. It should be noted that while a single processor is depicted inFIG. 1, in some other embodiments power-transfer monitoring device 110might comprise a plurality of processors.

Memory 131 stores data and executable instructions, includinginstructions and data corresponding to the methods of FIGS. 7 through 13described below, and may include volatile memory devices (e.g., randomaccess memory [RAM]), non-volatile memory devices (e.g., flash memory),and/or other types of memory devices. Clock 132 transmits the currenttime, date, and day of the week to processor 130 in well-known fashion.

In one embodiment, power-transfer monitoring device 110 comprises aprinted circuit board on to which landing points 120, sensor arrays 125and processor 130 are mounted. In some examples, each landing point120-i is a conductive printed pad comprising a two-dimensional cladplate that is soldered to sensor array 125-i and/or processor 130.Materials such as fiberglass, polyester, polymide, etc. may be used toprovide thermal insulation by which isolation and sensory independencebetween sensor arrays 125-1, 125-2, and 125-3 are maintained.

In one embodiment, processor 130 is capable of transmitting data signalsand control signals to electrical source 170 and is further capable ofreceiving signals from electrical source 170, as indicated in FIG. 1. Inone implementation, signals between processor 130 and electrical sourceare transmitted/received via a serial-interface data communication line.It should be noted that in some other embodiments, signals may betransmitted in one direction only, from processor 130 to electricalsource 170.

In one example, the control signals are ON/OFF binary signals capable ofcontrolling a safety relay of electrical source 170, and of interruptingpower delivery by electrical source 170. As described in detail below,data signals may include status information pertaining to safety,performance, carrying capacity, availability, etc. Operational statusmay be reported as a stream of data updates and may include, forexample, instantaneous system performance, safety status, voltage,frequency, current, ampacity, availability, time, historical events withtime-stamps, and so forth. The status reported may describe one ofseveral states—for example, system available, system unavailable, systemidle, system in use, system reserved, or system out-of-service withdiagnostic subcode for maintenance purposes. This status may change overtime as the system goes through repeated cycles of use.

Under normal safe operating conditions, processor 130 transmits acontrol signal that instructs electrical source 170 to continuesupplying power. When a potentially-hazardous condition is detected,processor 130 instead transmits a control signal (e.g., an exceptionflag, etc.) that instructs electrical source 170 to modulate,temporarily interrupt, or completely shut off the flow of power, asappropriate, based on the particular condition. In some implementationsthis functionality may be provided by an interruptive solid-state switchcircuit breaker, which can be tripped OFF (e.g., by injecting a tinyleakage current into the breaker's leak-detection or GFCI circuit.,etc.). In some other implementations, a relay contactor, voltagecontrol, or current control may be employed.

In one embodiment, processor 130 is further capable of transmitting datasignals and control signals to electrical load 190. In one example, datasignals transmitted to electrical load 190 may, like the data signalstransmitted to electrical source 170, include status informationpertaining to safety, performance, carrying capacity, availability, etc.Under normal safe operating conditions, the signals will indicatewhether or not electrical load 190 has permission to continue drawingpower (e.g., “OK to Charge”, “Do Not Charge Now”, etc.). In oneembodiment, the signals may also control the rate of power transfer(e.g., maximum, 25% reduction, 50% reduction, etc.), as well as timing(e.g., scheduled delays, periodic power transfer, etc.).

In some implementations, communications between processor 130 andelectrical load 190 are via a serial-interface data communication linethat is also capable of detecting and announcing when electrical load190 has been disconnected, and when some other electrical load has beenconnected. In some other implementations, an analog proportionalinterface or a pulse width modulation (PLM) time-based signal may beemployed in lieu of a serial interface.

Transceiver 140 is capable of receiving signals from one or more devices(e.g., a personal computer, a server, a wireless base station, anoff-board GPS receiver, etc.), and forwarding to processor 130 dataencoded in these signals (e.g., location-related data, time-relateddata, ambient characteristic data, etc.). Transceiver 140 is furthercapable of receiving data from processor 130, encoding the data insignals and transmitting the signals (e.g., transmitting sensor data toa remote computer system that performs monitoring, etc.)

In some embodiments, transceiver 140 may communicate with devices viawireless signals (e.g., RF signals, etc.), while in some otherembodiments transceiver 140 may communicate via wireline signals (e.g.,Ethernet, etc.), while in still other embodiments transceiver 140 mayemploy a plurality of communication technologies and/or protocols (forexample, Wi-Fi, Bluetooth, Ethernet, and CDMA). It will be appreciatedby those skilled in the art that in the latter case, monitoring devicemay comprise a plurality of transceivers rather than a singletransceiver. For convenience, however, this disclosure will simply referto transceiver 140, regardless of whether monitoring device comprises asingle transceiver or a plurality of transceivers.

In some embodiments, sensor arrays 125-1/125-2/125-3 might have the sameset of sensors, while in some other embodiments, sensor arrays125-1/125-2/125-3 might have different sets of sensors (e.g., the set ofsensors for one sensor array is a proper subset of the sensors ofanother sensor array; the set of sensors for one sensor array is aproper subset of the sensors of another sensor array, augmented with oneor more additional sensors not depicted in FIGS. 2 and 3; the set ofsensors for one sensor array and the set of sensors for another sensorarray are disjoint; etc.).

In accordance with some embodiments, the three sensor arrays might beuniform in attitude, while in some other embodiments, they may vary inattitude. For example, when the sensor arrays comprise optical sensors,which may have sensitive surfaces, it might be advantageous to orientthe sensor arrays at different angles, particular when they have narrowcones and/or limited focus (e.g., one up, one left, and one right;etc.). Similarly, in some embodiments the three sensor arrays might beuniform in environmental properties such as bandwidth, wavelength etc.),while in some other embodiments they may have different environments. Aswill be appreciated by those skilled in in the art, the particularchoice of attitudes/environments might be made in order to bring out aparticular quality that is relevant to the application (e.g., bandwidth,center frequency, etc.).

In addition, some embodiments may employ insulation and/or isolationbetween the sensor arrays. In the case of optical sensors, for example,opaque material might be placed in between the sensors, while foracoustic and/or vibration sensors, mechanical insulation and/orisolation might be employed, while for magnetic sensors, a magneticshield (e.g., mumetal, etc.) might be employed.

In some embodiments, electrical power-transfer system 100 may have thecapability to reverse the flow of power (a “two-way system”), so thatelectrical load 190 can be discharged during particular time intervalsin addition to being charged during other time intervals. Duringdischarge, power flows out of electrical load 190 toward electricalsource 170, thereby driving electrical source 170. Discharge may beuseful, for example, during a power outage when electrical source 170becomes disconnected from its power supply. For the case whereelectrical load 190 is an electrical vehicle, this discharge issometimes referred to as “V2G”. In one embodiment, the operation ofpower-transfer monitoring device 110 is unaffected by the direction ofpower flow, functioning in the same manner and equally well in bothdirections (e.g., in charging and discharging modes, etc.).

FIG. 2 depicts a block diagram of sensor array 125-i, as shown in FIG.1, in accordance with one embodiment of the present disclosure. As shownin FIG. 2, sensor array 125-i comprises: electrical sensor(s) 210-i,which are capable of obtaining measurements of one or more electricalproperties such as voltage, current, resistance, impedance, inductance,etc.; optical sensor(s) 215-i, which are capable of obtainingmeasurements of optical properties such as color, photosensitivity,intensity, etc.; magnetic sensor(s) 220-i, which are capable ofobtaining measurements of magnetic properties such as magnetic strength,dip (vertical inclination relative to gravity, consisting of magnitudein degrees and heading angle from magnetic north), direction (e.g.pitch/yaw/roll, etc.), polarity, etc.; chemical sensor(s) 225-i, whichare capable of obtaining measurements of chemical properties such as pH,flammability, salinity, etc.; environmental sensor(s) 230-i, which arecapable of obtaining measurements of various environmental properties,as described in detail below with respect to FIG. 3; location-basedsensor(s) 235-i, which are capable of obtaining measurements oflocation-related information such as geo-location and proximity via, forexample, a GPS receiver, an indoor wireless location system, etc.;orientation sensor(s) 240-i, which are capable of obtaining measurementssuch as attitude angle, pitch angle, gravimetric intensity, etc.;motion-based sensor(s) 245-i, which are capable of obtainingmeasurements such as speed, acceleration, etc.; vibration sensor(s)250-i, which are capable of obtaining measurements of mechanicalvibration such as magnitude, frequency, etc.; static field sensors255-i, which are capable of obtaining measurements of DC; and time-basedsensor(s) 260-i that are capable of establishing highly-precise timereferences of events (e.g., environmental events; the time-of-flight ofan injected pulse, which can be used to determine proximity; thereaching of thresholds, the occurrence of transitions, etc.).

It should be noted that in some embodiments, one or more of the abovedata may be obtained from a remote source instead of an on-board sensor,or in some instances by both an on-board sensor and remote source. Forexample, geo-location information might be obtained via transceiver 140from a location server or an off-board GPS receiver, either instead of,or in combination with location-based sensor(s) 235-i. It should furtherbe noted that in some alternative embodiments, sensor array 125-i mightcomprise a different set of sensors (e.g., a subset of the sensorsdepicted in FIG. 2, a superset of the sensors depicted in FIG. 2, a setof sensors consisting of a subset of the sensors depicted in FIG. 2 incombination with one or more additional sensors, etc.).

FIG. 3 depicts a block diagram of environmental sensors 230-i, as shownin FIG. 2, in accordance with one embodiment of the present disclosure.Environmental sensors 230-i comprises thermometer 310-i, which iscapable of obtaining temperature measurements, in well-known fashion;hygrometer 320-i, which is capable of obtaining humidity measurements,in well-known fashion; barometer 330-i, which is capable of obtainingbarometric pressure measurements, in well-known fashion; anemometer340-i, which is capable of obtaining measurements of wind speed anddirection, in well-known fashion; and radiation sensor 350-i, which iscapable of obtaining radiation level measurements (e.g., infrared,ultraviolet, visible light, radio frequency, microwave, millimeter wave,particle, alpha rays, beta rays, gamma rays, etc.).

As noted above for sensor array 125-i, in some embodiments some or allof the above environmental data may be obtained from a remote sourceinstead of, or in addition to, on-board sensor(s). It should further benoted that in some alternative embodiments, environmental sensors 230-imight comprise a different set of sensors (e.g., a subset of the sensorsdepicted in FIG. 3, a superset of the sensors depicted in FIG. 3, a setof sensors consisting of a subset of the sensors depicted in FIG. 3 incombination with one or more additional sensors, etc.).

The sensors in sensor arrays 125 can be divided into two classes:passive sensors, and active sensors. A passive sensor is noninvasive andobtains measurements silently, through observation only. Examplesinclude sensors in the set of electrical sensors 210 measuring voltageand current; sensors in the set of orientation sensors 240 measuringattitude, pitch, and gravimetric intensity; and so forth. An activesensor, in contrast, injects a stimulus (e.g., a radio frequency pulse,a DC potential voltage, an ultrasonic signal, etc.) and measures one ormore parameters of the response to the stimulus. Examples includesensors in the set of electrical sensors 210 that measure resistance andinductance; sensors in the set of time-based sensors 260 that measurethe time-of-flight of an injected pulse; and so forth.

FIG. 4 depicts a first example installation of power-transfer monitoringdevice 110 in accordance with one embodiment of the present disclosure.As shown in FIG. 4, the installation includes, interconnected as shown:power-transfer monitoring device 110, electrical source 170, electricalload 190, of FIG. 1; wall segment 410-1 housing a first portion of aconductor 480-1, a first portion of a conductor 480-2, a first portionof a conductor 480-3, and a first junction box 420-1; wall segment 410-2housing a second portion of conductor 480-1, a second portion ofconductor 480-2, a second portion of conductor 480-3, and a secondjunction box 420-2; wall segment 410-3 housing a third portion ofconductor 480-1, a third portion of conductor 480-2, a third portion ofconductor 480-3, and a third junction box 420-3 comprising an electricalreceptacle that can accommodate different appliance types and sizes andcan provide a disconnectable interface; conductors 180-1, 180-2, and180-3 connecting power-transfer monitoring device 110 to electricalsource 170; and conductors 185-1, 185-2, and 185-3 connectingpower-transfer monitoring device 110 to electrical load 190.

Wall segments 410 serve to isolate the conductors and protect them fromdamage, as well as to protect users in the facility who might otherwisecome into contact with them. In some examples the wall segments may beconcrete building foundations or outdoor earthwork, conduits, orconcrete sidewalks.

FIG. 5 depicts a flow diagram of aspects of a method 500 for detectingand handling a hazardous state of an electrical power-transfer system,in accordance with one embodiment of the present disclosure. The methodis described below with respect to electrical power-transfer system 100of FIG. 1; however the method may be performed with respect to someother system. In one embodiment, the method may be performed during oneor more of the following times: before electrical load 190 is connected,during transfer of power while electrical load 190 is connected, andafter completion of electrical load 190's power-transfer cycle. Itshould be noted that in some implementations, one or more blocksdepicted in FIG. 5 might be performed simultaneously, or in a differentorder than that depicted. In addition, while a single execution ofmethod 500 is depicted in FIG. 5, method 500 may be performed multipletimes (e.g., a pre-determined number of times, at fixed or variable timeintervals; in an infinite loop, etc.).

At block 501, a stimulus power signal is injected into electricalpower-transfer system 100. The power signal might be a single impulse, arepeated pulse, an active sensor probe, an uninterrupted continuoussignal such as an AC sine wave, etc. The particular choice of powersignal may be guided with the objective of eliciting a resonantresponse. It should be noted that two or more independent energizedinjections may overlap (e.g., normal operating current and an activesensor probe signal, etc.).

In some embodiments, the sensing cycle of a sensor comprises theinjection of a stimulus signal and subsequent measurement of the returnsignal. For example, a proximity sensor may actively inject a pulse intoits associated conductor and measure the time-of-flight for thereverberant pulse to return.

In accordance with one embodiment, the power signal is injected underthe control of power-transfer monitoring device 110 by commandingelectrical source 170 to connect to a source of electric-potential, andif loaded, to cause electric current to flow. This modulates the flow ofcurrent, which provides a stimulus that courses through thepower-transfer system 100 and acts as a probe. The modulation thusenables sensor arrays 125 to measure changes that are associated with orinduced by the power-transfer activity. As described below, theresultant signal returned to power-transfer monitoring device 110, whichis measured by sensor arrays 125, can expose and illuminate potentialhazards. An example impulse response characteristic for temperature andvoltage is shown in FIG. 7.

At block 502, processor 130 of power-transfer monitoring device 110receives one or more sensor measurements from one or more of sensorarrays 125-1, 125-2 and 125-3. In some examples, the sensor measurementsmay be made during the injection of the signal, while in some otherexamples the sensor measurements may be made after the injection of thesignal. In one embodiment, the sensor measurements are sampled, with thesampling being triggered by an interrupt. In some implementations theinterrupts might occur at fixed time intervals, while in some otherimplementations the interrupts might occur at variably-sized timeintervals. As will be appreciated by those skilled in the art, in someother embodiments sampling might be triggered by some other type ofevent, rather than an interrupt (e.g., by a detection of a change in asampled parameter or in a signal differential, etc.), while in stillother embodiments the sensor measurements might be received continuouslyor near-continuously.

At block 503, the sensor measurements received at block 502 areprocessed. In one embodiment, blocks 502 and 503 are both performed byprocessor 130 in response to a single interrupt or event. In some otherembodiments, blocks 502 and 503 might be performed in response toseparate, successive interrupts/events. In some implementations thesuccessive interrupts/events might be of different types, while in someother implementations the successive interrupts/events might be of thesame type.

In one embodiment, the processing of sensor measurements includes thecomputation of functions (e.g., proportional, integral, and derivativefactors; noise removal; imputation; prognostic projections andestimates; derivatives [e.g., first derivatives, second derivatives,etc.], averages, moving averages, etc.). In one implementation, datafrom sensor arrays 125-1, 125-2 and 125-3 are stored in athree-dimensional data structure, and successive instances of the datastructure are stored in a circular buffer. In one example, the circularbuffer is sufficiently large to hold data for a complete migration cycleto estimate the probability of an impending fault condition.

At block 504, processor 130 detects a hazardous state of electricalpower-transfer system 100 based on the processed sensor measurements. Inone embodiment, state includes one or both of (1) the state ofindividual components (e.g. conductors), and (2) the overall state ofelectrical power-transfer system 100 (e.g., availability, productivity,capacity, safety, etc.).

Hazardous states may be indicated or suggested by a variety ofconditions, such as variance in one or more conductors (e.g.,dimensional [cross-sectional] variance along a conductor, materialvariance between conductors [which can cause Ohmic variance], etc.)and/or physical changes in one or more conductors during operation(e.g., due to magnetic changes, vibration, thermal changes, elongationcontact, etc.).

In one embodiment, a variety of techniques may be used to detecthazardous states. One such technique is to compare one or more aspectsof the current state (e.g., conductor impedance, system capacity, etc.)to a baseline. For example, a baseline profile may be established fordiurnal cycles of observable characteristics that may affect systemperformance. These characteristics may show normal patterns of variancefrom nominal that can be predicted for example based on date and timeschedule or meteorological data. For example, the voltage, frequency,and reluctance of a source of power may be influenced by ambient thermalconditions on long utility lines and transformers that supply utilitypower over long distances. These may also be affected by incident solarradiation along the line. As another example, seasonal baseline profilemay be established. This may be useful in desert locations whichexperience more extreme variance between summer and winter conditions.

In some embodiments, baseline references may be adjusted based oninstantaneous sensor readings at the point of use, or on near-real-timemeteorological reports that are associated with deviations from thebaseline. For example, a rainstorm can induce observable changes in apower transmission line that affect power quality. Instantaneousobserved readings may deviate from an expected baseline. This varianceis range-checked, and used as predictive measure. Excessive variance maybe associated with an impending fault and may predict an imminentfailure condition. Using these techniques, the device can take action,temporarily reducing its load and reducing its exposure to fluctuations.This reduction can serve to isolate any influence from the appliance onthe power source, thus stabilizing the source, and also any connecteddistribution equipment that may be connected.

Another such technique is to identify when one or more aspects of systembehavior exhibit a particular pattern known to be associated withhazards (e.g., rapid changes in particular parameters, a change in therelationship between two or more parameters, departures from typicaldiurnal patterns, etc.). An example of a typical diurnal pattern isdepicted in FIG. 8, showing temperature over time. In accordance withone implementation, time-of-day phase angle measurements provide a moredirect measure of environmental thermal variance, which may includesolar exposure with local inumbration and reflection.

In some examples, the frequency of the sensing cycle may besignificantly higher than that of the flow modulations of the operatingcurrent (for example, a sensing cycle frequency of multiple times persecond, versus a flow modulation frequency of, for example, 6 kHz). Insuch examples, sensing cycles will occur when operating current flow isoff, when current is high, and when current is modulated at mid-level.Accordingly, two additional techniques may be used to detect hazardousstates: observing the differential between sensor measurements atvarious current levels, and observing the differential between sensormeasurements at different conductor pairs.

Power quality may be sensed through the waveforms of the single- andthree-phase power being transferred. The dynamic AC characteristics ofthe load may be adjusted in order to avoid excessive current spikes, orto take advantage opportunistically, to stabilize the source, or toisolate and protect the appliance from potential problems upstream.

In some embodiments, both active and passing sensing techniques may beused in conjunction, such that sensor arrays 125-1, 125-2, and 125-3 areindependently capable of active signal injection for active sensing(e.g., injecting a reference signal at a specific frequency between apair of conductors, etc.). In one example, a 20 kHz signal is injectedbetween sensor arrays 125-1 and 125-2 and the impedance between the twosensor arrays is measured. During the signal injection, two additionalimpedance measurements are made: one between sensor arrays 125-1 and125-3, and one between sensor arrays 125-2 and 125-3. The impedancemeasurements characterize different aspects of the conductiveenvironment, and can provide diagnostic clues that indicate pre-emergentfault conditions.

A second phase view may be obtained by injecting a 20 kHz signal betweensensor arrays 125-1 and 125-3 and measuring the impedance between thesetwo sensor arrays. In this second phase view, additional impedancemeasurements are made between sensor arrays 125-1 and 125-2, and betweensensor arrays 125-2 and 125-3. Similarly, a third phase view may beobtained by injecting a 20 kHz signal between sensor arrays 125-2 and125-3 and measuring the impedance between these two sensor arrays. Inthis third phase view, additional impedance measurements are madebetween sensor arrays 125-1 and 125-2, and between sensor arrays 125-1and 125-3.

Impedance between sensor array pairs is just one example of a propertythat can be actively measured (i.e., measured after signal injection).Other examples include Each of the phase views provides data from adifferent vantage point, and the overlap in viewpoint redundancy canpotentially provide both consistency checking and diagnostic capability(e.g., localizing a defect/fault to a particular conductor, or aparticular subset of conductors, etc.). For example, a galvaniccorrosion-induced fault condition may be visible from only oneparticular phase view. Suppose, for example, that corrosive contactexists between sensor arrays 125-2 and 125-3. The interface betweenthese two sensor arrays is measured actively in the third phase view,and is measured passively in the first and second phase views. Undernormal conditions (i.e., where there are no defects or faults),measurements would be symmetrical across all phase views. Under abnormalconditions, however, local geometry and chemistry, as well as thegeometry of a particular defect/fault may create asymmetrical signaturesthat can detect defects and existing faults, and predict future faults.Further, changes in measurements over time (e.g., changes in theimpedance measurements of the first phase view at two different times,changes in the differences between impendence measurements of the firstphase view and second phase view at two different times, etc.) may beused to estimate rate of corrosion and its hazardous criticality.

In accordance with one embodiment, measurements are logged, and the logmay be used to guide subsequent off-line diagnostic analysis. Thediagnostic records can be provided for external analysis by a humantechnician, or may also be analyzed algorithmically. For example, thecurrent invention (power-transfer monitor) may spend most of its servicelife monitoring a power system that never experiences a failure or ashut-down event. Monitoring may be performed continuously over longperiods of time. The frequency of fault events can be zero but theincidence of suboptimal but subclinical detections or interventionsthrough modulation may be significantly greater than zero. In thesesystems, the record of subclinical event occurrences provides aprognostic alarm that can detect the early onset of system degradationslong before any failure occurs. Patterns detected in the log ofsubclinical events can recommend maintenance procedures veryspecifically, and can guide service that designates specific componentsfor replacement, repair, or refurbishment. This is valuable inapplications that are exposed to high-severity failure modes, forexample in vehicular, aerospace, and weapons applications. Powermonitoring over a long service history provides a deep view into devicelife to improve serviceability, reliability, and operational confidence.In the most mission-critical or risk-sensitive applications, thetolerance for modulation interventions can be set to zero or near-zero.This retains a full capability for modulation to gracefully degradeperformance during an anomaly, but uses a modulation event to trigger oractivate a maintenance procedure or replacement. This can provide forexample a “limp-home” capability that continues to deliver power at alower performance level until the service can be completed. Then after aservice procedure has been performed, the monitor serves to verifyoperational capability at the start of a new service life. In someembodiments, passive sensing from multiple phase views can be employed,either in conjunction with sensing from multiple phase views, or on itsown (i.e., without multiple-phase-view active sensing). For example, inthe case of grounded single-phase, three conductors may be sensedthermally, with conductor pairs compared.

It should be noted that the multiple-phase-view technique disclosedabove can be performed in a similar fashion when there are four sensorsarrays/conductor pairs (e.g., for a three-phase circuit, etc.), or whenthere is an even greater number of sensors arrays/conductor pairs, bothwith active sensing and/or passive sensing. It should be noted that insome embodiments, one or more of blocks 502, 503, and 504 may occurwithin a monitoring loop not depicted in the flow diagram.

At block 505, one or more remedial actions are taken in response to thehazardous state identified at block 504 are identified. Action is takenprogrammatically to avoid the problem; the information that enableddetection often describes a rich context that has good diagnosticspecificity. This diagnostic detail may be useful to inform subsequentremedial actions. Remediation may for example be applied as repairs,maintenance, or replacement. In this case, the diagnostic informationfrom an event is stored with the event record in memory 131, recalledand presented through status device 150 to a user.

Two classes of automatic or programmatic action that may be applied aresafety shutoff and modulation. Safety shutoff is invoked when a clearand present hazard is detected, indicating that operation is unsafe.Modulation may be invoked when conditions indicate a developing orimpending hazardous condition that is trending away from normal safeoperating conditions. This is used to avoid a problem and reverse theobserved operating variance, and automatically return to normaloperating conditions. It should be noted that not all conditions can bereversed by modulation: for example, corrosion or wear may be beyond thecapability of modulation. In these cases, modulation provides a“graceful degradation” to continue operation without necessitating ashutdown. Continued operation even in a degraded state still has highvalue, especially in high-reliability systems where downtime may beexpensive or even catastrophic (e.g., in aircraft and flight systems,etc.). The farthermost modulation extreme may achieve zero or near-zerocurrent, with correspondingly zero power transfer. This case is similarto a safety shutoff, except that conductors 180 & 185 remain energized,and some minimal level of appliance functionality is maintained.

In one embodiment, the modulation is implemented in a power conversiondevice within load 190, and is performed in response to a signal frommonitoring device 110. The power conversion device may be an AC/DCconverter that converts the variable line voltage (AC 1-phase or AC3-phase or DC) to the specific power needs for the load's internal use.This internal need usually includes a DC battery.

In one embodiment, one or more modulation techniques may be employed,such as pulse width modulation (PWM), frequency modulation (FM), phasemodulation (PM), amplitude modulation (AM), or some combination thereof.Each of these modulation techniques constitutes a dimension that isdescribed or prescribed parametrically, and may be described as “loadquality modulation.”

In one embodiment, three-phase modulation may be employed. To transferpower in three-phase AC form, an appliance must be connected to allthree of the power phases. The benefits of three-phase power oversingle-phase power include improved stability, constant power over time,equilateral grounding, etc. The three phases may be three sine wavesspaced 120 degrees, carrying a constant power capacity.

Power from a three phase line may be converted into a format that ismost favorable for consumption or end-use. When an energy storage deviceor battery is used, direct current is a common format. To convert fromthe three-phase power transfer mechanism into the internally-preferredDC, the three conductors may be connected to three inverters as follows:conductors 185-1 and 185-2 are connected as an input pair to a firstinverter; conductors 185-2 and 185-3 are connected as an input pair to asecond inverter; and conductors 185-1 and 185-3 are connected as aninput pair to a third inverter.

During operation of power-transfer system 100, processor 130 maydiscover a fault, anomaly, unbalance, or other suboptimal condition.This detection may be made in the sensor data streams that originate insensor arrays 125-1, 125-2, and 125-3 (e.g., via some characteristicpattern identified in the sensor signals, etc.). The presence or absenceof the pattern in the sensor streams may enable location to betriangulated down to a single conductor, either 185-1, 185-2, or 185-2.An example of a geographically local fault is corrosion that has formedalong the conductive metal pathway, leaking current outside the circuit,or restricting the normal flow current inside the circuit. The fault maybe present on only one single conductor of the three, with the other twoconductors free of any anomaly or problem.

As is described in detail below, defects/faults may be localized viarotating perspective viewpoint relative to an injected sensor signal.These two directional vectors can be thought of as a viewing angle andan angle of illumination. Varying the included angle between these twoenhances perceptive power to detect and localize problems.

When sensing has detected an anomaly, perspective sensing and rotatingviews may be used to narrow down its location spatially or logically.Once the anomaly's location is known, mitigating action can beprescribed with pinpoint accuracy. Action may be implemented bydifferential modulation in the power conversion layer of the appliance.Actions may be taken that appear as a graceful degradation inperformance, thereby enabling continuity of operation and avoiding theneed for an abrupt safety stop.

In one embodiment, action is taken by differentially modulating the loadprofiles on converter/inverter pairs: when an anomaly is located in asingle conductor, only the conversion devices that are connected to thatconductor are modulated. In one implementation, the modulation is achange in the current profile (amperes over time), and only conversiondevices that are connected to the affected conductor are modulated. Theremaining conversion device that is not connected to the impactedconductor is not modulated, and continues operation unimpeded.

As an example, consider the case where sensor arrays data indicates thepresence of an anomaly. Once the anomaly is detected processor 130 usesmultiple sensor viewpoints to localize the anomaly to a single affectedconductor, in this case 185-3. Processor 130 forwards the inferredlocation of to load 190, where control actions are implemented. Thesecond and third inverters are subjected to a modulation of their loadprofiles. This may reduce the peak current or the power conducted onconductor 185-3. The first inverter may be commanded to continue itsoperation unimpeded, and conductors 185-2 and 185-1 experience nomodulation or degradation.

The power carried by conductors 185-2 and 185-1 is the sum of all threephase currents. While two of the phases are modulated, the availablecarrying capacity of the remaining phase current is proportionallyincreased. This enables recovery of some of the capacity lost byreducing the capacity of the affected conductor 185-3.

If and when the sensor arrays detect that an anomaly has passed, themodulation profile restrictions can be eased. This allows the system tolift its modulated state and return to unrestricted functionality.Transitions between these states are performed automatically undersoftware control.

Multi-conductor sensing, combined with three-phase power transfer,provides a synergistic alignment of perceptive power and prescriptivespecificity. This resonant match-up extends the beneficial capabilitiesof the invention favorably.

In one embodiment, the particular modulation technique(s) are selecteddynamically based on the particular hazardous state that has beendetected. In one implementation, sensor data are associated with thehazardous state to prescribe an appropriate modulation technique that iscommunicated to the power conversion device and performed during powerconversion. The system is pre-programmed with a set of modulationresponses to respond to particular hazardous states (e.g., the mostcommon hazardous states, etc.). The risk of the sensed hazard may beestimated from sensed data, and the degree of the modulation responsemay be prescribed in proportion to the hazard risk (e.g., a proportionalrelationship between the degree of modulation and a “hazardous stateseverity scale” from 1 to 10, etc.).

For example, in a three-phase system, a reduction in impedance maydevelop between conductors 185-2 and 185-3, as detected by sensor arrays(125-1, 125-2, 125-3, and 125-3). The reduction may be a variance from adesign specification, or from a calibrated value, or from a historicallog that is unique to the device. This condition of reduced-impedancemay be caused for example by accumulation of corroded material or othersolid or liquid contamination between conductors 180-2, 180-3, 185-2and/or 185-3, or by a variety of other environmental factors. Note thatthere are several permutations of conductor pairs where deviance can bemeasured and detected.

The sensed reading deviates from its expected value in the direction ofzero. Readings are made at the sensor arrays 125-1, 125-2, 125-3, and125-3 and communicated to Processor 130. Software running in Processor130 uses the communicated readings to calculate an instantaneousDeviationRatio, as:DeviationRatio=1−(ExpectedImpedance−MeasuredImpedance)/ExpectedImpedance).This yields a Ratio as a positive fractional value between 0 and 1 (0%and 100%). This fraction is transformed into a modulation command andcommunicated to Electrical Load 190, which interprets the command forimplementation. Because this in this example corrosive deviance wasdetected between conductor pair 185-2 and 185-3, the modulation isapplied to Inverter 192, which is fed by the same two conductors 185-2and 185-3. Inverter 192 implements the command by modulating its loadprofile, for example by reducing the duty cycle of its PWM(pulse-width-modulated) load. This causes a reduction in the RMS currentcarried by Inverter 192. The remaining two inverters 191 and 193 are notaffected by this modulation, and remain functional at their fullcapacity. The current carried by Conductor 185-1 is not affected by thismodulation but conductors 185-2 and 185-3 experience a reduction intheir RMS current. This reduces the stress level on corrosion-impactedconductors 185-2 and 185-3 and on their nearby electrical environment.This has the effect of avoiding the risk of a failure event that mightbe associated with this corrosion. The modulation event is logged forfuture review for remediation or maintenance service. This review mightfor example recommend cleaning the area between conductors 185-2 and185-3, or replacing contacts, insulation, or conductor material. Thecycle is accomplished with no failure event, and no need to shut downthe system, which remains functional and operational continuously inspite of the modulation. This process localizes the affected regionaccurately and takes action automatically and rapidly with no need forhuman attention or intervention, and without shutting down the system.

In one embodiment, the system determines whether the hazardous state hasbeen corrected (e.g., transformed into an non-hazardous state, etc.) bythe modulation response. If the modulation failed to correct thehazardous state, then a safety shutdown is performed.

A safety shutoff event may require an inspection or other manualsupervisory function before permission is given to resume safeoperation. It may also require a minimum time interval to allow calmingor cool-down before restoring operation. Depending on the nature orseverity of the fault condition, an inspection may be required. This mayinclude a manual visual or electrical inspection to verify that nodamage has occurred. The inspection process may also be fully automatic,implemented through sensor arrays 125-1, 125-2, 125-3. All sensor arraysare independently operable, and remain fully functional while ElectricalSource 170 is offline, and when Electrical Load 190 is off-line. Thisallows for their autonomous operation for purposes of pre-inspection andsafety qualification.

After block 505 has been performed, method 500 terminates. As describedabove, although a single execution of method 500 is depicted in FIG. 5,the method may be performed multiple times (e.g., a pre-determinednumber of times, at fixed or variable time intervals; in an infiniteloop, etc.).

In one embodiment, method 500 may be performed during a “servicesession,” in which (1) electrical load 190 is connected conductively,(2) power is then transferred or consumed, and (3) electrical load 190is then disconnected, ending the session. When electrical load 190 is amobile appliance, its mobility is restored once the session has ended.An example of a power-transfer cycle during a service session is shownin FIG. 9.

Concepts employed in the techniques disclosed above (i.e., for detectinga hazardous state, performing one or more remedial actions in responseto the detection of the hazardous state, and diagnosing a cause of thehazardous state) can also be employed for other types of undesirablestates in an electrical power-transfer system. Such undesirable statesmay include suboptimal states (e.g., power delivery that is less thanthe maximum capability of the electrical power-transfer system, or isless than a threshold percentage of the maximum capability [for exampleless than 80% of maximum], etc.) distortions in power line quality,variance in power line quality above a particular threshold, underload,overload, etc. A method for detecting and handling such undesirablestates is disclosed below and with respect to FIG. 6.

FIG. 6 depicts a flow diagram of aspects of a method 600 for detectingand handling an undesirable state of an electrical power-transfer system(e.g., distortions in power line quality, variance in power line qualityabove a particular threshold, underload, overload, etc.), in accordancewith one embodiment of the present disclosure. Method 600 is describedbelow with respect to electrical power-transfer system 100 of FIG. 1;however the method may be performed with respect to some other system.In one embodiment, method 600 may be performed during one or more of thefollowing times: before electrical load 190 is connected, duringtransfer of power while electrical load 190 is connected, and aftercompletion of electrical load 190's power-transfer cycle. It should benoted that in some implementations, one or more blocks depicted in FIG.6 might be performed simultaneously, or in a different order than thatdepicted. In addition, while a single execution of method 600 isdepicted in FIG. 6, method 600 may be performed multiple times (e.g., apre-determined number of times, an infinite loop, etc.)

At block 601, a stimulus power signal is injected into electricalpower-transfer system 100. The power signal might be a single impulse, arepeated pulse, an active sensor probe, an uninterrupted signal such asan AC sine wave, etc. The particular choice of power signal may beguided with the objective of eliciting a resonant response. It should benoted that two or more independent energized injections may overlap(e.g., normal operating current and an active sensor probe signal,etc.).

In some embodiments, the sensing cycle of a sensor comprises theinjection of a stimulus signal and subsequent measurement of the returnsignal. For example, a proximity sensor may actively inject a pulse intoits associated conductor and measure the time-of-flight for thereverberant pulse to return.

In accordance with one embodiment, the power signal is injected underthe control of power-transfer monitoring device 110 by commandingelectrical source 170 to connect to a source of electric-potential, andif loaded, to cause electric current to flow. This modulates the flow ofcurrent, which provides a stimulus that courses through thepower-transfer system 100 and acts as a probe. The modulation thusenables sensor arrays 125 to measure changes that are associated with orinduced by the power-transfer activity. As described below, theresultant signal returned to power-transfer monitoring device 110, whichis measured by sensor arrays 125, can expose and illuminate potentialhazards. An example impulse response characteristic for temperature andvoltage is shown in FIG. 7.

At block 602, processor 130 of power-transfer monitoring device 110receives one or more sensor measurements from one or more of sensorarrays 125-1, 125-2 and 125-3. In one embodiment, the sensormeasurements are sampled, with the sampling being triggered by aninterrupt. In some implementations the interrupts might occur at fixedtime intervals, while in some other implementations the interrupts mightoccur at variably-sized time intervals. As will be appreciated by thoseskilled in the art, in some other embodiments sampling might betriggered by some other type of event, rather than an interrupt (e.g.,by a detection of a change in a sampled parameter or in a signaldifferential, etc.), while in still other embodiments the sensormeasurements might be received continuously or near-continuously.

At block 603, the sensor measurements received at block 602 areprocessed. In one embodiment, blocks 602 and 603 are both performed byprocessor 130 in response to a single interrupt or event. In some otherembodiments, blocks 602 and 603 might be performed in response toseparate, successive interrupts/events. In some implementations thesuccessive interrupts/events might be of different types, while in someother implementations the successive interrupts/events might be of thesame type. In one embodiment, the processing of sensor measurementsincludes the computation of functions (e.g., proportional, integral, andderivative factors; noise removal; imputation; prognostic projectionsand estimates; derivatives [e.g., first derivatives, second derivatives,etc.], averages, moving averages, etc.). In one implementation, datafrom sensor arrays 125-1, 125-2 and 125-3 are stored in athree-dimensional data structure, and successive instances of the datastructure are stored in a circular buffer. In one example, the circularbuffer is sufficiently large to hold data for a complete migration cycleto estimate the probability of an impending fault condition.

At block 604, processor 130 detects a undesirable state of electricalpower-transfer system 100 based on the processed sensor measurements. Inone embodiment, state includes one or both of (1) the state ofindividual components (e.g. conductors), and (2) the overall state ofelectrical power-transfer system 100 (e.g., availability, productivity,capacity, safety, etc.).

Undesirable states may be indicated or suggested by a variety ofconditions, such as variance in one or more conductors (e.g.,dimensional [cross-sectional] variance along a conductor, materialvariance between conductors [which can cause Ohmic variance], etc.)and/or physical changes in one or more conductors during operation(e.g., due to magnetic changes, vibration, thermal changes, elongationcontact, etc.).

In one embodiment, a variety of techniques may be used to detectundesirable states. One such technique is to compare one or more aspectsof the current state (e.g., conductor impedance, system capacity, etc.)to a baseline. For example, a baseline profile may be established fordiurnal cycles of observable characteristics that may affect systemperformance. These characteristics may show normal patterns of variancefrom nominal that can be predicted for example based on date and timeschedule or meteorological data. For example, the voltage, frequency,and reluctance of a source of power may be influenced by ambient thermalconditions on long utility lines and transformers that supply utilitypower over long distances. These may also be affected by incident solarradiation along the line. As another example, seasonal baseline profilemay be established. This may be useful in desert locations whichexperience more extreme variance between summer and winter conditions.

In some embodiments, baseline references may be adjusted based oninstantaneous sensor readings at the point of use, or on near-real-timemeteorological reports that are associated with deviations from thebaseline. For example, a rainstorm can induce observable changes in apower transmission line that affect power quality. Instantaneousobserved readings may deviate from an expected baseline. This varianceis range-checked, and used as predictive measure. Excessive variance maybe associated with an impending fault and may predict an imminentfailure condition. Using these techniques, the device can take action,temporarily reducing its load and reducing its exposure to fluctuations.This reduction can serve to isolate any influence from the appliance onthe power source, thus stabilizing the source, and also any connecteddistribution equipment that may be connected.

Another such technique is to identify when one or more aspects of systembehavior exhibit a particular pattern known to be associated withhazards (e.g., rapid changes in particular parameters, a change in therelationship between two or more parameters, departures from typicaldiurnal patterns, etc.). An example of a typical diurnal pattern isdepicted in FIG. 8, showing temperature over time. In accordance withone implementation, time-of-day phase angle measurements provide a moredirect measure of environmental thermal variance, which may includesolar exposure with local inumbration and reflection.

In some examples, the frequency of the sensing cycle may besignificantly higher than that of the flow modulations of the operatingcurrent (for example, a sensing cycle frequency of multiple times persecond, versus a flow modulation frequency of, for example, 6 kHz). Insuch examples, sensing cycles will occur when operating current flow isoff, when current is high, and when current is modulated at mid-level.Accordingly, two additional techniques may be used to detect undesirablestates: observing the differential between sensor measurements atvarious current levels, and observing the differential between sensormeasurements at different conductor pairs.

Power quality may be sensed through the waveforms of the single- andthree- phase power being transferred. The dynamic AC characteristics ofthe load may be adjusted in order to avoid excessive current spikes, orto take advantage opportunistically, to stabilize the source, or toisolate and protect the appliance from potential problems upstream.

In some embodiments, both active and passing sensing techniques may beused in conjunction, such that sensor arrays 125-1, 125-2, and 125-3 areindependently capable of active signal injection for active sensing(e.g., injecting a reference signal at a specific frequency between apair of conductors, etc.). In one example, a 20 kHz signal is injectedbetween sensor arrays 125-1 and 125-2 and the impedance between the twosensor arrays is measured. During the signal injection, two additionalimpedance measurements are made: one between sensor arrays 125-1 and125-3, and one between sensor arrays 125-2 and 125-3. The impedancemeasurements characterize different aspects of the conductiveenvironment, and can provide diagnostic clues that indicate pre-emergentfault conditions.

A second phase view may be obtained by injecting a 20 kHz signal betweensensor arrays 125-1 and 125-3 and measuring the impedance between thesetwo sensor arrays. In this second phase view, additional impedancemeasurements are made between sensor arrays 125-1 and 125-2, and betweensensor arrays 125-2 and 125-3. Similarly, a third phase view may beobtained by injecting a 20 kHz signal between sensor arrays 125-2 and125-3 and measuring the impedance between these two sensor arrays. Inthis third phase view, additional impedance measurements are madebetween sensor arrays 125-1 and 125-2, and between sensor arrays 125-1and 125-3.

Impedance between sensor array pairs is just one example of a propertythat can be actively measured (i.e., measured after signal injection).Other examples include Each of the phase views provides data from adifferent vantage point, and the overlap in viewpoint redundancy canpotentially provide both consistency checking and diagnostic capability(e.g., localizing a defect/fault to a particular conductor, or aparticular subset of conductors, etc.). For example, a galvaniccorrosion-induced fault condition may be visible from only oneparticular phase view. Suppose, for example, that corrosive contactexists between sensor arrays 125-2 and 125-3. The interface betweenthese two sensor arrays is measured actively in the third phase view,and is measured passively in the first and second phase views. Undernormal conditions (i.e., where there are no defects or faults),measurements would be symmetrical across all phase views. Under abnormalconditions, however, local geometry and chemistry, as well as thegeometry of a particular defect/fault may create asymmetrical signaturesthat can detect defects and existing faults, and predict future faults.Further, changes in measurements over time (e.g., changes in theimpedance measurements of the first phase view at two different times,changes in the differences between impendence measurements of the firstphase view and second phase view at two different times, etc.) may beused to identify rate of corrosion and its undesirable criticality.

In accordance with one embodiment, measurements are logged, and the logmay be used to guide subsequent off-line diagnostic analysis. Thediagnostic records can be provided for external analysis by a humantechnician, or may also be analyzed algorithmically. Further, the gainof the preset response may be tuned or otherwise adjusted to better ormore quickly respond to observed conditions.

In some embodiments, passive sensing from multiple phase views can beemployed, either in conjunction with sensing from multiple phase views,or on its own (i.e., without multiple-phase-view active sensing). Forexample, in the case of grounded single-phase, three conductors may besensed thermally, with conductor pairs compared.

It should be noted that the multiple-phase-view technique disclosedabove can be performed in a similar fashion when there are four sensorsarrays/conductor pairs (e.g., for a three-phase circuit, etc.), or whenthere is an even greater number of sensors arrays/conductor pairs, bothwith active sensing and/or passive sensing. It should be noted that insome embodiments, one or more of blocks 602, 603, and 604 may occurwithin a monitoring loop not depicted in the flow diagram.

At block 605, one or more remedial actions are taken in response to theundesirable state identified at block 604 are identified. Action istaken programmatically to avoid the problem; the information thatenabled detection often describes a rich context that has gooddiagnostic specificity. This diagnostic detail may be useful to informsubsequent remedial actions. Remediation may for example be applied asrepairs, maintenance, or replacement. In this case, the diagnosticinformation from an event is stored with the event record in memory 131,recalled and presented through status device 160 to a user.

Two classes of automatic or programmatic action that may be applied aresafety shutoff and modulation. Safety shutoff is invoked when a clearand present hazard is detected, indicating that operation is unsafe.Modulation may be invoked when conditions indicate a developing orimpending undesirable condition that is trending away from normal safeoperating conditions. This is used to avoid a problem and reverse theobserved operating variance, and automatically return to normaloperating conditions. It should be noted that not all conditions can bereversed by modulation: for example, corrosion or wear may be beyond thecapability of modulation. In these cases, modulation provides a“graceful degradation” to continue operation without necessitating ashutdown. Continued operation even in a degraded state still has highvalue, especially in high-reliability systems where downtime may beexpensive or even catastrophic (e.g., in aircraft and flight systems,etc.). The farthermost modulation extreme may achieve zero or near-zerocurrent, with correspondingly zero power transfer. This case is similarto a safety shutoff, except that conductors 180 & 185 remain energized,and some minimal level of appliance functionality is maintained.

In one embodiment, the modulation is implemented in a power conversiondevice within load 190, and is performed in response to a signal frommonitoring device 110. The power conversion device may be an AC/DCconverter that converts the variable line voltage (AC 1-phase or AC3-phase or DC) to the specific power needs for the load's internal use.This internal need usually includes a DC battery.

In one embodiment, one or more modulation techniques may be employed,such as pulse width modulation (PWM), frequency modulation (FM), phasemodulation (PM), amplitude modulation (AM), or some combination thereof.Each of these modulation techniques constitutes a dimension that isdescribed or prescribed parametrically, and may be described as “loadquality modulation.”

In one embodiment, the particular modulation technique(s) are selecteddynamically based on the particular undesirable state that has beendetected. In one implementation, sensor data are associated with theundesirable state to prescribe an appropriate modulation technique thatis communicated to the power conversion device and performed duringpower conversion. The system is pre-programmed with a set of modulationresponses to respond to particular undesirable states (e.g., the mostcommon undesirable states, etc.). The degree of the modulation responsemay be determined based on the magnitude of the undesirable state (e.g.,a linear relationship between the degree of modulation and a“undesirable state severity scale” from 1 to 10, etc.).

In one embodiment, the system determines whether the undesirable statehas been corrected (e.g., transformed into an non-undesirable state,etc.) by the modulation response. If the modulation failed to correctthe undesirable state, then a safety shutdown is performed.

A safety shutoff event may require an inspection or other manualsupervisory function before permission is given to resume safeoperation. It may also require a minimum time interval to allow calmingor cool-down before restoring operation. Depending on the nature orseverity of the fault condition, an inspection may be required. This mayinclude a manual visual or electrical inspection to verify that nodamage has occurred. The inspection process may also be fully automatic,implemented through sensor arrays 125-1, 125-2, 125-3. All sensor arraysare independently operable, and remain fully functional while ElectricalSource 170 is offline, and when Electrical Load 190 is off-line. Thisallows for their autonomous operation for purposes of pre-inspection andsafety qualification.

After block 605 has been performed, method 600 terminates. As describedabove, although a single execution of method 600 is depicted in FIG. 5,the method may be performed multiple times (e.g., a pre-determinednumber of times, at fixed or variable time intervals; in an infiniteloop, etc.).

In one embodiment, method 600 may be performed during a “servicesession,” in which (1) electrical load 190 is connected conductively,(2) power is then transferred or consumed, and (3) electrical load 190is then disconnected, ending the session. When electrical load 190 is amobile appliance, its mobility is restored once the session has ended.An example of a power-transfer cycle during a service session is shownin FIG. 9.

In accordance with one embodiment, electrical load 190 is augmented withadditional functionality, or “intelligence”. In one example, theintelligent load is capable of detecting a second load on the samecircuit. Large loads, such as EV charging stations, air conditioners,washers, dryers, electric stoves, etc. are ideally on their own circuitwith an appropriately rated breaker. However, this is not alwayspossible due to installation costs, limitations to the panel size, orthe home electric service feed. Various hardware solutions have evolvedto enable the sharing of the same circuit between loads; however, thesesolutions can be costly. It would be advantageous if an added load weresufficiently intelligent to detect that it is being used in a sharedcircuit situation, and in response to this detection, automaticallythrottle or turn off its own energy use when it detects another loadcomes online. We disclose such a load (subsequently referred to as a“smart load”) below.

In accordance with one embodiment, a smart load continuously monitorsthe voltage of the circuit to which it is connected. The smart loadobserves and persists the voltage drop that results from its ownoperation (original voltage when idle minus new voltage when fullyoperational). The smart load further observes and persists thetemperature increase caused by heat dissipation on the circuit wiressupplied by remote sensing.

In one embodiment, the smart load will enter a transitional statewhenever a voltage drop of similar magnitude is observed either prior toor during its own operation. The smart load will not permit activeoperation when the temperature of the wires is elevated, and/or when thetemperature of the wires matches previously observed values under load.The smart load will turn off (e.g., in a single step, in successivesteps, etc.) and will confirm that the circuit voltage has recovered. Itwill continue to monitor the heat dissipation on the circuit wiresthrough remote sensing.

The smart load will only resume operation if it registers a voltageincrease that matches the previously registered decrease. It will waituntil the circuit wires have sufficiently cooled which serves as anadditional confirmation that no other load is active.

The smart load thus enables, for example, the addition of a smart EVcharger to a dryer circuit. This smart charger would have the capabilityto detect the presence of another load on the same circuit and modifyits own operation to accommodate this load.

It is to be understood that the above-described embodiments are merelyillustrative of the present invention and that many variations of theabove-described embodiments can be devised by those skilled in the artwithout departing from the scope of the invention. It is thereforeintended that such variations be included within the scope of thefollowing claims and their equivalents.

What is claimed is:
 1. A method comprising: injecting an electricalsignal into an electrical power-transfer system, wherein the electricalpower-transfer system comprises an electrical power source, anelectrical load, a first sensor, a second sensor, a third sensor, afirst conductor, a second conductor, and a third conductor, and whereinthe first sensor is electrically coupled to the second sensor and thefirst conductor, and wherein the second sensor is electrically coupledto the third sensor and the second conductor, and wherein the thirdsensor is electrically coupled to the third conductor; measuring, duringor after the injection of the electrical signal, (1) an electricalproperty between the first sensor and the second sensor to obtain afirst measurement, (2) the electrical property between the second sensorand the third sensor to obtain a second measurement, and (3) theelectrical property between the first sensor and the third sensor toobtain a third measurement; determining that the electricalpower-transfer system is in a hazardous state based on the firstmeasurement, the second measurement, and the third measurement; and inresponse to the determining that the electrical power-transfer system isin the hazardous state, performing one or more actions to correct thehazardous state.
 2. The method of claim 1 wherein the electricalproperty is impedance.
 3. The method of claim 1 further comprisingidentifying the first conductor as a cause of the hazardous state basedon at least one of the first measurement, the second measurement, or thethird measurement.
 4. The method of claim 1 wherein the electricalsignal is injected between the first sensor and the second sensor. 5.The method of claim 1 wherein the electrical signal is injected inresponse to a signal transmitted to the electrical power source.
 6. Themethod of claim 5 wherein the signal is transmitted to the electricalpower source by an electrical monitoring device that further receivesmeasurements from the first sensor.
 7. The method of claim 1 wherein theone or more actions comprises modulating current in the electricalpower-transfer system.
 8. The method of claim 7 wherein the modulatingfails to correct the hazardous state, and wherein the one or moreactions further comprises a shutoff of power, and wherein the shutoff isin response to the modulating failing to correct the hazardous state. 9.A method comprising: injecting a first electrical signal into anelectrical power-transfer system, wherein the electrical power-transfersystem comprises an electrical power source, an electrical load, a firstsensor, a second sensor, a third sensor, a first conductor, a secondconductor, and a third conductor, and wherein the first sensor iselectrically coupled to the second sensor and the first conductor, andwherein the second sensor is electrically coupled to the third sensorand the second conductor, and wherein the third sensor is electricallycoupled to the third conductor; measuring, during or after the injectionof the first electrical signal, an electrical property between the firstsensor and the second sensor to obtain a first measurement; injecting asecond electrical signal into the electrical power-transfer system;measuring, during or after the infection of the second electricalsignal, the electrical property between the second sensor and the thirdsensor to obtain a second measurement; determining that the electricalpower-transfer system is in a hazardous state based on the firstmeasurement and the second measurement; and in response to thedetermining that the electrical power-transfer system is in thehazardous state, performing one or more actions to correct the hazardousstate.
 10. The method of claim 9 wherein the electrical property is DCresistance.
 11. The method of claim 9 wherein the first electricalsignal is a continuous signal.
 12. The method of claim 9 furthercomprising selecting one of the first conductor, the second conductor,or the third conductor as a cause of the hazardous state as on at leastone of the first measurement or the second measurement.
 13. The methodof claim 9 wherein the first electrical signal is injected between thefirst sensor and the second sensor, and wherein the second electricalsignal is injected between the second sensor and the third sensor. 14.The method of claim 9 wherein the one or more actions comprisesmodulating current in the electrical power-transfer system.
 15. Themethod of claim 14 wherein the modulating fails to correct the hazardousstate, and wherein the one or more actions further comprises a shutoffof power, and wherein the shutoff is in response to the modulatingfailing to correct the hazardous state.
 16. The method of claim 9further comprising estimating a rate of corrosion based on the firstmeasurement and the second measurement.
 17. A method for detecting andhandling a suboptimal state of an electrical power-transfer system,wherein the electrical power-transfer system comprises an electricalpower source, an electrical load, a first sensor, a second sensor, athird sensor, a first conductor, a second conductor, and a thirdconductor, and wherein the first sensor is electrically coupled to thesecond sensor and the first conductor, and wherein the second sensor iselectrically coupled to the third sensor and the second conductor, andwherein the third sensor is electrically coupled to the third conductor,and wherein the method comprises: measuring, by the first sensor, anenvironmental property to obtain a first measurement; measuring, by thesecond sensor, the environmental property to obtain a secondmeasurement; measuring, by the third sensor, the environmental propertyto obtain a third measurement; determining that the electricalpower-transfer system is in the suboptimal state based on the firstmeasurement, the second measurement, and the third measurement;identifying a proper subset of the first conductor, the secondconductor, and the third conductor as a cause of the suboptimal state;and in response to the determining that the electrical power-transfersystem is in the suboptimal state, performing one or more actions tocorrect the suboptimal state.
 18. The method of claim 17 wherein thesuboptimal state is one or overload or underload.
 19. The method ofclaim 17 wherein the environmental property is one of temperature,humidity, or pressure.
 20. The method of claim 17 wherein the one ormore actions comprises modulating current in the electricalpower-transfer system.